1. Field of the Invention
The present invention relates to a planar light emitting device, and more particularly to a planar light emitting device in which a substrate mounted with a light source is provided insertably and removably from a side surface of the device.
2. Description of the Related Art
As a light source, such as a liquid crystal backlight, a planar light emitting device is used that emits light from a point light source such as a light emitting diode in a planar shape. The planar light emitting device is configured to cause light from at least one light emitting diode to enter into one end surface of a light guide plate having a position facing main surfaces and to emit the light from the whole of one of the main surfaces of the light guide plate.
As such a planar light emitting device, for example, JP2007-311327A discloses a planar light source device including a plurality of point light sources; a light guide plate that emits incident light from the point light sources to one side surface from an emission surface; a lower case having a side surface formed substantially in parallel with an incident surface of the light guide plate; and a light source substrate on which the plurality of point light sources are placed at predetermined intervals, and that is placed on a side of the incident surface of the light guide plate, wherein a substrate holding member is provided that holds the light source substrate and the side surface of the lower case with a protrusion placed between the two point light sources.
Generally, a planar light emitting device has a structure in which a light source substrate mounted with a light source can be attached or detached so that a light source that fails can be easily replaced. JP2007-311327A discloses a structure in which the light source substrate is inserted into and removed from the side surface of the planar light emitting device. However, in JP2007-311327A, a screw or a substrate holding member needs to be removed from an upper surface or a lower surface to remove the light source substrate. For this purpose, a display device or a machine to which the planar light emitting device is mounted needs to be disassembled so that the upper surface or the lower surface is visible, which requires a large number of steps for removing the light source substrate.
JP2007-311327A also discloses a structure without a screw for fixing the light source substrate or a substrate holding member, but this structure requires clearance for removing the light source substrate, and the clearance reduces heat dissipation to the lower case (rear sheet metal) as compared with the structure in which the light source substrate is fixed to the lower case. Thus, heat generated by light emission is not released to increase the temperature of the point light source and therearound to reduce the reliability (life) and brightness of the point light source.